Envelope doesn't influence VCA

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ivo francx
 
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Envelope doesn't influence VCA

Post by ivo francx »

Hey,

So I've almost finished my x0x, exept for one little detail.
When playing, the notes sustain forever. So I'm thinking this is because there is something wrong with the envelope generator. Though as soon as I turn up the env mod pot, the envelope starts to influence the behaviour of the filter. So that indicates that there could be something wrong with the VCA. Unfortunately, all my efforts to find an error where unsuccsessful up to now. So my question is: Has anyone ever had this or a similar problem? Any ideas what to check next?

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antto
 
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Re: Envelope doesn't influence VCA

Post by antto »

the VCA uses a sepparate envelope generator (not the main one which is used for the VCF)

go to keyboard mode and press down some note for ~10 seconds - it should decay down

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ivo francx
 
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Re: Envelope doesn't influence VCA

Post by ivo francx »

Nope, didn't work... I've even tried holding the buttons longer than 10 seconds. But still no stopping the VCA...

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ivo francx
 
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Re: Envelope doesn't influence VCA

Post by ivo francx »

Could you point out where the second envelope generator is located? I'm kinda having a hard time finding it.

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antto
 
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Re: Envelope doesn't influence VCA

Post by antto »

it's C42, located in the VCA section
it generates a Decay envelope (with fixed time) which is applied thru Q31 into the opamps (IC15)

it's supposed to fade away for roughly 5-7seconds

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mmm
 
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Re: Envelope doesn't influence VCA

Post by mmm »

Check the voltage at the cathode of D27 when playing a note. This should give you the proper envelope voltage before it enters the current mirror.

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